I'm not familiar with Asus' return/defect policies, but with Dell Ultrasharps, they're very very tolerant with returns. I've had single dead pixels and they replaced it. They sent me a new monitor first with a prepaid shipping label, and UPS comes and picks it up from your house.

The input lag on both of them seem to be the same, within 1ms of each other. Honestly though, if response time + input lag is important important because you're gaming competitively, you'll want a 120hz TN with as minimal input lag as possible.
I was even considering getting a separate CRT monitor just for gaming, HAH!